1. Field of the Invention
The present invention relates to an illumination device used for a liquid crystal display apparatus and the like.
2. Description of the Related Art
As compared with a CRT, a display contrast (dynamic range) of a liquid crystal display apparatus is lower and an improvement therein is desired. For example, Japanese Patent Application Publication, Tokukai, No. 2002-99250 discloses a liquid crystal display apparatus wherein a plurality of illumination areas, each of which has a luminance that is individually controllable, is formed in a backlight device. The liquid crystal display apparatus thereby controls luminance of each of the illumination areas of the backlight device according to luminance and darkness of an image displayed in a liquid crystal panel. This liquid crystal display apparatus controls the luminance of the illumination areas so that the luminance is high in the illumination area corresponding to a display area where a bright image is displayed while the luminance is low in the illumination area corresponding to the display area where a dark image is displayed. A display dynamic range is thereby enlarged and the liquid crystal display apparatus thus realizes a display with a high sense of contrast.
Here, as illustrated in FIG. 22, Japanese Patent Application Publication, Tokukai, No. 2002-99250 discloses a backlight device 112 including: a plurality of illumination areas that include cold cathode fluorescent tubes 101 and white LEDs (not illustrated) as light sources; and a separation wall 102 partitioning each of the illumination areas.
However, there is a problem in the backlight device 112 of FIG. 22. The backlight device 112 can prevent leakage of light (cross talk) between the illumination areas by the separation wall 102. On the other hand, in the case where the luminance is individually controlled in each of the illumination areas, variations in wavelength of the white LED in each of the illumination areas cause the emission of uneven luminance or uneven color in the vicinity of the separation wall. Such a problem stands out when LEDs with high color reproducibility corresponding to R, G, and B, respectively are used as light sources. This causes the degradation in a display quality.